I really do like my 10-22mm EF-S, a truly useful lens, with quite good build quaility, but I do not have a 17-85mm, so it is difficult for me to say what you would be missing by not having the 10mm to 17mm zoom range. Keep in mind that ultra-wide images which try to "take it all in" can be empty and boring, so try to learn about using ultra-wides before the holiday. An ultra-wide is more for getting close to a subject, than trying to record an image of half the world, at distance, with one click. I am certainly not discouraging you from the 10-22mm!

Upon further reflection, compared to a kit zoom lens which starts at 18mm, with which I am familiar, I believe my 10-22mm is truly useful, though build quality and pride of ownership are part of that equation. Another lens I had considered, the 15-85mm, has an excellent reputation among members of this forum. 15mm, with the 1.6 crop factor, is equivalent in field-of-view to a 24mm on "full" frame. On a full-frame camera, 24mm is started to become really wide, though not what is generally termed ultra-wide. Ultra-wide-angle lenses are an acquired taste. If possible, perhaps try one that is borrowed, rented, or hired, before purchasing?

First let me start by saying I have none of what we are talking about except the T2i But from my studying for future purchases I'll give you my opinion.

The super wides like to 10-22 take special learning and care to use. It is not something that a normal person can pickup and jump right into perfect pictures. It doesn't work like you expect. If you are truly considering it, I would rent it first.

Your 17-85, I have been told and read, is basically the 18-55 kit lens but goes out to 85. If you really want to consider a new wide lens, look at the 15-85. Gordon has told me a few times that the diff between 17 and 15 doesn't sound like a lot but at these low ends do make a lot of difference. Also, the image quality and build of the 15-85 is comparable to an L lens just without weather sealing.